Presumed Metastasis of Breast Cancer to the Abducens Nucleus Presenting as Gaze Palsy

A 51-year-old woman with breast cancer presented with progressive diplopia. Neuro-ophthalmologic examination revealed right gaze palsy and peripheral facial nerve palsy. Brain magnetic resonance imaging (MRI) was normal. However, two months later a repeat brain MRI revealed an enhancing round nodular mass at the right facial colliculus of the lower pons, at the location of the abducens nucleus. Localized metastasis to the abducens nucleus can cause gaze palsy in a patient with breast cancer.